4... g8f6  5. b1c3  5... a7a6  6. d4b3 The ultimate prophylactic move. White takes the knight out before the thematic e7-e5, which is fundamentally Black's plan after a7-a6. The move is still possible, but it's a bit discouraging to play it when your opponent has already taken the knight out of d4. 6... e7e6 Probably the most logical move, leading to a Scheveningen pawn structure. Kasparov would certainly approve.